Various types of industrial machinery, automation equipment, vehicles, robots, mechanical devices having artificial intelligence (AI), etc. have electric motors for transmitting rotation power. Such a motor has been developed from a direct current (DC) motor whose rotor consists of a coil into a brushless DC (BLDC) motor whose rotor consists of a permanent magnet.
In such a motor, demagnetization in which the magnetic force of a magnet weakens according to a change in temperature occurs. Within a predetermined temperature range, reversible demagnetization occurs so that magnetic flux may return to its original state when the temperature returns to its original value. However, when the temperature exceeds a predetermined value, irreversible demagnetization in which magnetic flux does not return to its original state occurs, and the life span of the motor shortens.
For this reason, according to the related art, a temperature sensor is attached inside a motor to measure the temperature. In this case, due to an additional circuit configuration and wiring, the cost and volume of the motor increase, and also the complexity of the motor increases. In addition, since the motor has a small space therein, it may be difficult to install the temperature sensor, and wrong information may be obtained when a signal line of the temperature sensor is closed or opened.